V3:
- Rebased against latest dmaengine/next tree.
- Updated API doc with new kernel version and dates.
- Changed to allow driver to load without ENQCMD support.
- Break out some patches that can be sent ahead of this series for inclusion.
v2:
- Dropped device feature enabling (GregKH)
- Dropped PCI device feature enabling (Bjorn)
- https://members.pcisig.com/wg/PCI-SIG/document/14237
- After some internal discussion, we have decided to hold off on the enabling
of DMWR due to the
following reasons. 1. Most first gen hw will not have the feature bits. 2.
First gen hw that
support the feature are all Root Complex integrated endpoints. 3. PCI devices
that are not
RCiEP’s with this capability won’t surface for a few years so we can wait
until we can test the
full code.
- Dropped special ioremap (hch)
- Added proper support for WQ flush (tony, dan)
- Changed descriptor submission to use sbitmap_queue for blocking. (dan)
Driver stage 1 postings for context: [1]
The patch series has compilation and functional dependency on Fenghua's "Tag
application
address space for devices" patch series for the ENQCMD CPU command enumeration
and the PASID MSR
support. [2]
First patch in the series is only there to assist with compilation. Can be
dropped once Fenghua’s
series is accepted by the x86 maintainers.
== Background ==
A typical DMA device requires the driver to translate application buffers to
hardware addresses,
and a kernel-user transition to notify the hardware of new work. Shared Virtual
Addressing (SVA)
allows the processor and device to use the same virtual addresses without
requiring software to
translate between the address spaces. ENQCMD is a new instruction on Intel
Platforms that allows
user applications to directly notify hardware of new work, much like how
doorbells are used in
some hardware, but it carries a payload along with it. ENQCMDS is the
supervisor version (ring0)
of ENQCMD.
== ENQCMDS ==
Introduce enqcmds(), a helper funciton that copies an input payload to a 64B
aligned
destination and confirms whether the payload was accepted by the device or not.
enqcmds() wraps the new ENQCMDS CPU instruction. The ENQCMDS is a ring 0 CPU
instruction that
performs similar to the ENQCMD instruction. Descriptor submission must use
ENQCMD(S) for shared
workqueues (swq) on an Intel DSA device.
== Shared WQ support ==
Introduce shared workqueue (swq) support for the idxd driver. The current idxd
driver contains
dedicated workqueue (dwq) support only. A dwq accepts descriptors from a
MOVDIR64B instruction.
MOVDIR64B is a posted instruction on the PCIe bus, it does not wait for any
response from the
device. If the wq is full, submitted descriptors are dropped. A swq utilizes
the ENQCMDS in
ring 0, which is a non-posted instruction. The zero flag would be set to 1 if
the device rejects
the descriptor or if the wq is full. A swq can be shared between multiple users
(kernel or userspace) due to not having to keep track of the wq full condition
for submission.
A swq requires PASID and can only run with SVA support.
== IDXD SVA support ==
Add utilization of PASID to support Shared Virtual Addressing (SVA). With PASID
support,
the descriptors can be programmed with host virtual address (HVA) rather than
IOVA.
The hardware will work with the IOMMU in fulfilling page requests. With SVA
support,
a user app using the char device interface can now submit descriptors without
having to pin the
virtual memory range it wants to DMA in its own address space.
The series does not add SVA support for the dmaengine subsystem. That support
is coming at a
later time.
[1]:
https://lore.kernel.org/lkml/157965011794.73301.15960052071729101309.st...@djiang5-desk3.ch.intel.com/
[2]: https://lkml.org/lkml/2020/6/30/1266
[3]: https://software.intel.com/en-us/articles/intel-sdm
[4]:
https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
[5]:
https://software.intel.com/en-us/download/intel-data-streaming-accelerator-preliminary-architecture-specification
[6]: https://01.org/blogs/2019/introducing-intel-data-streaming-accelerator
[7]: https://intel.github.io/idxd/
[8]: https://github.com/intel/idxd-driver idxd-stage2
---
Dave Jiang (5):
x86/asm: move the raw asm in iosubmit_cmds512() to special_insns.h
x86/asm: add enqcmds() to support ENQCMDS instruction
dmaengine: idxd: add shared workqueue support
dmaengine: idxd: clean up descriptors with fault error
dmaengine: idxd: add ABI documentation for shared wq
Fenghua Yu (1):
x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions
Documentation/ABI/stable/sysfs-driver-dma-idxd | 14 ++
arch/x86/include/asm/cpufeatures.h | 1
arch/x86/include/asm/io.h | 45 +++++---
arch/x86/include/asm/special_insns.h | 17 +++
arch/x86/kernel/cpu/cpuid-deps.c | 1
drivers/dma/Kconfig | 13 ++
drivers/dma/idxd/cdev.c | 47 ++++++++
drivers/dma/idxd/device.c | 91 ++++++++++++++-
drivers/dma/idxd/dma.c | 9 --
drivers/dma/idxd/idxd.h | 26 ++++
drivers/dma/idxd/init.c | 91 ++++++++++++---
drivers/dma/idxd/irq.c | 143 ++++++++++++++++++++++--
drivers/dma/idxd/registers.h | 14 ++
drivers/dma/idxd/submit.c | 33 +++++-
drivers/dma/idxd/sysfs.c | 127 +++++++++++++++++++++
15 files changed, 602 insertions(+), 70 deletions(-)
--
